Molecular 'switch' connects biology to silicon

A molecular “switch” that can translate biological signals into electrical ones has been developed by scientists.

An international team from the UK, France, Italy, the Netherlands, and the Czech Republic developed the switch, which is made from a strand of DNA, an enzyme and a magnetic polystyrene bead. They say it could one day be used in biosensors and sophisticated human implants.

In their experimental setup, the switch consists of a strand of DNA stretched across the interior of a 0.1-millimetre-wide channel etched into a thin sheet of glass. One end of the DNA is anchored to one side of the channel.

The DNA has an enzyme attached to its anchoring base and a magnetic polystyrene bead attached to its free end. The whole switch sits in an inert liquid contained by the channel. DNA was used because it can be genetically engineered to attach easily to all of these components.

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The switch is triggered when a specific molecule passing through the liquid-filled channel binds to the enzyme at the DNA’s base. This activates the enzyme, causing it to pull the strand toward it, moving the magnetic bead at its end. Magnetic sensors within the channel’s walls detect this movement and produce an electrical signal. Watch a video simulation showing the process in action, here.

Reel it in

The researchers used an enzyme extracted from bacteria, which is triggered by the molecule Adenosine Triphosphate (ATP). Since all organisms use ATP to transport energy inside their cells, this switch could provide a useful interface between biological and electronic systems, says Keith Firman, a biotechnologist at Portmouth University, UK, who worked on the project.

Large pulses of ATP are released when muscles contract, for example. “I could see it providing an interface between muscle and implanted devices” or prosthetics, he adds. More immediately, the researchers hope to develop simple biosensors using the trigger.

The team tried slightly different enzyme sensors, capable of identifying other types of molecule and some of which could be reset after triggering. “It was important to ensure we were not tied to one ‘motor’,” Firman says.

Richard Nichols, an electrochemist at Liverpool University, UK, who was not involved with the work, says the DNA sensor could be used to control a wide range of biological implants. But he says it would work much more slowly than a conventional electronic circuit. “This device sounds like it has potential,” he says. “But my feeling is that the speed might not be that quick.